1. Field of the Invention
The present invention relates to an absorption chiller that uses an aqueous salt solution as an absorbent, water as a refrigerant, comprising an evaporator, a condenser, and absorber having heat exchanger tubes, respectively, and more particularly, to heat exchanger tubes to be installed inside the evaporator, condenser, and absorber.
2. Background Art
An absorption chiller generally allows an evaporator to exchange heat between brine flowing through a heat exchanger tube and refrigerant, and a condenser to exchange heat between cooling water flowing through a heat exchanger tube and refrigerant. Concave and convex features are provided on the outer surface of the heat exchanger tube for refrigerant to adhere and spread on the surface, and thus promote heat exchange between refrigerant and brine or cooling water flowing through the tubes. Projections, for example, shown in FIGS. 14 and 15, are known as concave and convex features. A heat exchanger tube 1X shown in FIG. 14 is provided, on the outer surface thereof, with mutually parallel fins 11. These fins serve to increase the outer surface area of the tube and thus improve the heat exchange property.
On the other hand, a heat exchanger tube 1X shown in FIG. 15 is provided with fins 12 in the same manner as fins 11 shown in FIG. 14. The fin 12 is provided, on a top thereof, with a first notch 13 that extends in the direction orthogonal to the direction of extension of the top of the fins. The fin 12 is also provided, on the top thereof, with a second notch 14 in such a manner that the apex is divided into two parts. This allows the surface area on the outer surface of the tube to increase more than that of the heat exchanger tube 1X shown in FIG. 14.
Some heat exchanger tubes have an increased surface area by providing the first notch 13 of the heat exchanger tube 1X shown in FIG. 15 at an angle of 40 to 60 degrees in the direction of extension of the top.
However, these heat exchanger tubes are only focused on increasing the surface area of the outer surface of the tube. For this reason, a large amount of liquid will make thicker layer in complicated deep concave portions outside the tube when refrigerant of water or absorbent are sprayed, trickled, or flown onto the heat exchanger tube in an absorption chiller that uses, for example, an aqueous salt solution such as lithium bromide as an absorbent and water as a refrigerant.
The refrigerant of water and absorbent thus thicker layer will become thermal resistance to deteriorate the heat transfer performance, so that this has given the problems that the function of evaporating refrigerant on the surface of the heat exchanger tube of the evaporator, the function of condensing steamed refrigerant on the surface of the heat exchanger tube of the condenser, and the function of absorbing refrigerant by means of absorbent on the surface of the heat exchanger tube of the absorber deteriorated respectively.
Also given has been another problem that building up of refrigerant of water or absorbent in concave portions caused liquid to spread on the outside the tube badly, so that a thick layer of water or absorbent built up outside the tube and thus deteriorated the heat transfer performance.